Immigration enforcement efforts actually have become more lax since the September 11 attacks and have had “no meaningful impact” on the growing number of immigrants now in the United States — which has reached a record high of 34 million, according to a report released yesterday.

A 13 percent increase of U.S. immigrants, more than 4 million, since 2000 included more than 2 million illegal aliens, who now total about 10 million or 30 percent of the immigrant population, the Washington-based Center for Immigration Studies (CIS), said in its report, based on as-yet-unpublished U.S. Census Bureau data.

The report said that while visa applicants from some parts of the world may have to wait longer for approval and a “tiny number of illegal aliens from selected countries” may have been detained, enforcement efforts did not constitute any major change in U.S. immigration policy.

The fact that immigration has remained so high, the report said, also showed that immigration totals are not tied to the nation’s economy, as some immigration proponents and others have suggested.

“The idea that immigration is a self-regulating process that rises and falls in close step with the economy is simply wrong,” said Steven Camarota, CIS director of research and the report’s author. “Today, the primary sending countries are so much poorer than the United States, even being unemployed in America is still sometimes better than staying in one’s home country.”

Mr. Camarota said the countries primarily represented among the nation’s immigrant population are much poorer than the primary sending countries in the past. The United States’ much higher standard of living, he said, exists even during recessions, noting that people come to the United States to join family, to avoid social or legal obligations, to take advantage of the United States’ social services, and to enjoy greater personal and political freedom.

“Even a prolonged economic downturn is unlikely to have a large impact on immigration levels. If we want lower immigration levels it would require enforcement of immigration laws and changes to the legal immigration system,” he said.

Maryland was among the eight states with the largest increases in immigrant population, along with Texas, Georgia, North Carolina, New Jersey, Washington, Arizona and Pennsylvania.

The report comes just two days after President Bush assured Mexico he would expend “political capital” earned in his re-election to push hard to grant temporary guest-worker status to millions of illegal immigrants now in the United States.

Mr. Bush has tried since the first month of his presidency in 2001 to push an immigration-reform bill through Congress that would allow illegal aliens to remain in this country indefinitely, and others to cross the border from Mexico, if they registered for “temporary worker cards.”

CIS, a private research organization that seeks better immigration enforcement, said in the report that the 34.24 million immigrants, both legal and illegal, now in the United States is the highest number ever recorded in American history. It said about half, or 2 million, of the 4.3 million increase since 2000 is estimated to be illegal aliens.

Data collected by the Census Bureau, the report said, showed there are roughly 9 million illegal aliens now in the United States, but that prior research found that 10 percent of the nation’s illegal-alien population is missed by the Census Bureau survey, suggesting a total illegal population of about 10 million in March of this year.

Mr. Camarota said the same Census Bureau data also showed that in the years between 2000 and 2004, nearly 6.1 million new immigrants — legal and illegal — arrived from abroad, but that the arrivals are offset by deaths and return migration among immigrants already here, so the total increased by 4.3 million.

He said the 6.1 million new immigrants who arrived since 2000 compared to 5.5 million new arrivals in the four years prior to 2000, during an economic expansion.

“The pace of immigration is so surprising because unemployment among immigrants increased from 4.4 to 6.1 percent, and the number of unemployed immigrants grew by 43 percent,” Mr. Camarota said.

The report also said:

 Unlike current immigration, evidence from the 19th and early 20th centuries indicates that economic downturns in this country did have a very significant effect on immigration levels.

 As a share of the nation’s total population, immigrants now account for nearly 12 percent, the highest percentage in more than 80 years.

 Recent immigration has had no significant effect on the nation’s age structure. If the 6.1 million immigrants who arrived after 2000 had not come, the average age in the United States would be virtually unchanged at 36 years.

 The diversity of the immigrant population continues to decline, with the top country, Mexico, accounting for 31 percent of all immigrants in 2004, up from 28 percent in 2000, 22 percent in 1990 and 16 percent in 1980.

The report is titled “Economy Slowed, But Immigration Didn’t: The Foreign-born Population 2000-2004,” and is available at the CIS Web site: www.cis.org.